1. Field of the Invention
The present invention relates to foamed acidizing fluids, additives for foaming the acidizing fluids and methods of acidizing subterranean zones.
2. Description of the Prior Art
The treatments of subterranean hydrocarbon containing formations penetrated by well bores with aqueous acidizing fluids to stimulate the production of hydrocarbons therefrom are well known to those skilled in the art. One such acidizing treatment involves the introduction of an aqueous acidizing fluid into the subterranean formation under pressure so that the acidizing fluid flows through the pore spaces of the formation. The acidizing fluid reacts with acid soluble materials contained in the formation thereby increasing the size of the pore spaces and the permeability of the formation.
Another production stimulation treatment known as fracture-acidizing involves the formation of one or more fractures in the formation and the introduction of an aqueous acidizing fluid into the fractures to etch the fractures faces whereby flow channels are formed when the fractures close. The aqueous acidizing fluid also enlarges the pore spaces in the fracture faces and in the formation.
In carrying out acidizing and fracture-acidizing treatments in subterranean zones, the acidizing fluid utilized must often be lightweight to prevent excessive hydrostatic pressure from being exerted on the subterranean zone. As a result, a variety of lightweight acidizing fluids have heretofore been developed and used including foamed acidizing fluids. In addition to being lightweight, a foamed acidizing fluid contains compressed gas which improves the ability of the acidizing fluid to backflow out of a subterranean zone which has been acidized or fracture-acidized and recovered.
Foamed acidizing and fracture-acidizing fluids have heretofore included various surfactants which function to facilitate the foaming of the fluids and stabilize the foams formed when gases are mixed therewith. However, the heretofore used foaming and foam stabilizing surfactant additives have not met complete environmental requirements. That is, when the foaming and stabilizing surfactants find their way into water in the environment, they do not fully degrade which can result in interference with aquatic lifecycles.
Thus, there are needs for improved foamed acidizing fluids, improved acidizing fluid foaming and stabilizing additives which are harmless to the environment and improved methods of acidizing subterranean zones.
The present invention provides improved foamed acidizing fluids for acidizing or fracture-acidizing subterranean zones, improved acidizing fluid foaming and stabilizing additives which are harmless to the environment and improved methods of acidizing or fracture-acidizing subterranean zones which meet the needs described above and overcome the deficiencies of the prior art. The improved foamed acidizing fluids are basically comprised of an aqueous acid solution, sufficient gas to form a foam and an effective amount of an environmentally harmless additive for foaming and stabilizing the gelled aqueous acid solution comprised of hydrolyzed keratin.
The aqueous acid solution foaming and stabilizing additive of this invention which is harmless to the environment is hydrolyzed keratin. The additive is preferably dissolved in water to form an aqueous solution which is added to the aqueous acid solution to be foamed along with a gas for foaming the aqueous acid solution.
The methods of the present invention for acidizing or fracture-acidizing subterranean zones penetrated by well bores are basically comprised of the following steps. A foamed acidizing fluid is prepared comprised of an aqueous acid solution, sufficient gas to form a foam and an effective amount of an additive for foaming and stabilizing the gelled aqueous acid solution comprised of hydrolyzed keratin. Thereafter, the subterranean zone is contacted with the foamed acidizing fluid.